Cross-Linked Foam Having a Shock-Absorbing Means for an Insole of Shoes

ABSTRACT

The present invention provides a cross-linked foam having a shock-absorbing means for an insole of shoes comprises a cross-linked foam body; an inner cavity structure formed in the cross-linked foam body, the inner cavity structure formed simultaneously with the cross-linked foam body; and a filler in the inner cavity structure. The filler may be filled into and sealed by a housing that is formed in the inner cavity structure. According to the present invention, the shock-absorbing means having a greater thickness than the cross-linked foam body can easily be formed in the cross-linked foam body and the inner cavity structure can be shaped along a shape of a bare foot to offer more comfortable fitting.

TECHNICAL FIELD

The present invention relates to a cross-linked foam, and more specifically a cross-linked foam having a shock-absorbing means for an insole of shoes that can be manufactured by a simple manufacturing process and effectively serves to reduce an impact applied to a foot.

BACKGROUND ART

We usually spend most of the time standing with shoes on feet. The shoe was developed to protect the bare feet of men. However, an importance of the shoes has been increasingly emphasized nowadays. Accordingly, the function of the shoes has been improved to protect a spinal column, a knee joint and an ankle joint as well as the feet.

Therefore, the shoe makers have been trying to give various function to mid-sole and out-sole contacting the ground and uppers contacting the feet. However not many researches have been made in the field to improve insole contacting the feet directly and delivering the impact to the feet. Recently, various models using an air tube have been suggested to improve a human sensation of the shoes by reducing the impact applied to the feet or increasing a contact property with the feet. Most of the suggestions are about methods in which a housing formed of flexible film type material is filled with an air and then inserted or attached to the insole to improve a function of shock-absorption of the insole. These methods may be regarded as a progressive technology in that they utilizes a property of an air as a shock-absorbing means by inserting or attaching the housing filled with the air to the insole. However, those methods have some disadvantages as follows.

FIG. 11 is a plan view of an insole according to the related art and FIG. 12 is a cross-sectional view of an insole taken along a line A-A′ of FIG. 11. Generally, an insole 10 mainly comprises a body 12 having a thickness Δt and an edge portion 16 formed along sides of the body 12. The edge portion 16 is tapered in a way that a thickness becomes smaller as it goes to an edge. The edge portion slopes up considering a form of the feet.

A reference number 18 in the figure is a finishing material such as a cloth and a non-woven fabric attached to the body 12.

The housing is usually formed of flexible material to maximize a shock-absorbing function of the air filled therein. Once the housing is filled with the air, a form of the housing is changed and deformed according to a pressure applied to the housing.

According to related art, the housing having a three-dimensional shape must be attached to the planar insole, but the housing cannot easily be attached to the insole owing to a difference of the shape. This problem becomes more serious considering the housing is likely to be deformed by an external pressure. Even if the housing is attached to the insole through a complex process and a high cost, the housing is likely to be separated from the insole during a use of the shoe owing to a repeated bending of the insole.

Meanwhile, it is a very tricky work to insert the housing having a relatively great thickness into the insole having a relatively small thickness Δt in FIG. 12. This problem becomes more serious considering that the housing must be located on the insole at a position 14 in FIG. 12 corresponding to the metatarsus and be extended to an edge portion of the insole having a very small thickness

In an alternative to overcome those problems, a certain portion of the formed body to which the housing is attached may be depressed or the housing may be disposed between two sheets of formed material at a proper position and then the two sheets of formed material are attached together. This method has following disadvantages.

Because this method requires an additional process and materials, a manufacturing cost becomes increased. Besides, because the insole around the housing is anfractuous, a human sensation of the shoes is bad and a durability of the insole cannot be secured.

DISCLOSURE OF INVENTION Technical Problem

Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and an object of the present invention is to provide a cross-linked foam for insole that can fulfill a shock-absorbing function without attachment or insertion of an additional shock-absorbing device to the insole.

Another object of the present invention is to provide a cross-linked foam for insole of which filler can stably fulfill a shock-absorbing function in the insole.

Another object of the present invention is to provide a cross-linked foam for insole of which shock-absorbing means can be formed in any portion of the insole.

Another object of the present invention is to provide a cross-linked foam for insole of which shock-absorbing means is formed in the insole simultaneously with the insole so that it offers more comfortable fitting.

Another object of the present invention is to provide a cross-linked foam for insole of which shock-absorbing means can be stably kept in the insole so that a durability can be improved.

Technical Solution

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a cross-linked foam for an insole for shoes comprises a cross-linked foam body having at least one inner cavity structure, the inner cavity structure formed in the cross-linked foam body; a housing in the inner cavity structure, the housing filled with filler.

In the above, the inner cavity structure having the housing may be formed in the cross-linked foam body at a position corresponding to a metatarsus of a foot.

In the above, unevenness may be formed on a covering portion of the inner cavity structure.

In the above, the cross-linked foam body may further have at least one inner cavity structure other than the inner cavity structure having the housing.

In the above, the cross-linked foam body may further have a plurality of inner cavity structures other than the inner cavity structure having the housing.

In the above, all or some of the plural inner cavity structures may be connected to each other.

In the above, at least one of the inner cavity structures other than the inner cavity structure having the housing is filled with filler.

In the above, the filler may be filled into the housing and the housing may be disposed in the inner cavity structure.

In the above, the filler may be selected from at least one of gas, liquid and material that is same as or different from the cross-linked foam body.

In the above, unevenness may be formed on a covering portion of at least one of the inner cavity structures other than the inner cavity structure having the housing.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

ADVANTAGEOUS EFFECTS

According to the present invention, a shock-absorbing means having a greater thickness than a cross-linked foam body can easily be formed in the cross-linked foam body at a predetermined position.

The shock-absorbing means can be formed in an inner cavity structure formed simultaneously with the cross-linked foam body without damaging a cross-linked foam. And therefore, the shape of the cross-linked foam can be maintained without any damage or deformation.

In addition, a human sensation of shoes can be greatly improved by filling certain material into the inner cavity structure or into a housing disposed in the inner cavity structure.

The inner cavity structure can be shaped along a shape of a bare foot to improve a human sensation of shoes and the insole having an effective shock-absorbing function can be provided with a low manufacturing cost.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a plan view of an insole having a shock-absorbing means according to the present invention;

FIG. 2 is a cross-sectional view of an insole taken along a line B-B′ of FIG. 1;

FIG. 3 is a cross-sectional view of an insole taken along a line C-C′ of FIG. 1;

FIG. 4 is a perspective view of a shock-absorbing means according to the present invention;

FIGS. 5 to 10 are illustrating a manufacturing process of an insole having a shock-absorbing means according to the present invention;

FIG. 11 is a plan view of an insole according to the related art; and

FIG. 12 is a cross-sectional view of an insole taken along a line A-A′ of FIG. 11.

MODE FOR THE INVENTION

Reference will now be made in detail to the preferred embodiment of the present invention, which is illustrated in the accompanying drawings.

FIG. 1 is a plan view of an insole having a shock-absorbing means according to the present invention, FIG. 2 is a cross-sectional view of an insole taken along a line B-B′ of FIG. 1 and FIG. 3 is a cross-sectional view of an insole taken along a line C-C′ of FIG. 1. A cross-linked foam 100 of the present invention mainly comprises a cross-linked foam body 120 and inner cavity structures 124 and 128. The cross-linked foam body 120 is formed by a cross-linked foaming method. The cross-linked foam body 120 can be manufactured by foaming various foaming material known in the field by various foaming method known in the field. Ethylene-vinyl acetate (EVA) based resin having diverse vinyl acetate contents (VA %) or polyethylene (PE) based resin having diverse density may desirably be selected as a raw material for the foaming material. However, the foaming material is not confined to those materials.

The inner cavity structure is formed in the cross-linked foam body 120 simultaneously with the cross-linked foam body 120. That is, the cross-linked foam body 120 and the inner cavity structure are foamed at a time. The inner cavity structure 128 for a metatarsus is desirably formed in the cross-linked foam body 120 at a position corresponding to the metatarsus of the feet. Though a shape of the inner cavity structure 128 for the metatarsus is not confined to a certain shape, a covering portion 126 of the inner cavity structure 128 for the metatarsus is desirably formed along an outline of the metatarsus of the feet so that a human sensation of the shoes can be greatly improved.

There may be formed another inner cavity structure other than the inner cavity structure for the metatarsus in the cross-linked foam body 120 at a position corresponding to a bottom of the feet. The shape and number of the additional inner cavity structure can be changed diversely according to a given condition. In FIG. 2, a single inner cavity structure 124 except the inner cavity structure for the metatarsus is formed in the cross-linked foam body 120, i.e. insole, at a position of a middle-foot. In FIG. 3, plural inner cavity structures 124 except the inner cavity structure for the metatarsus are formed in the cross-linked foam body 120, at a position of a fore-foot.

All or some of the additional inner cavity structures may be connected to each other or the additional inner cavity structure may be connected only to the adjacent additional inner cavity structure. The connected structure of the inner cavity structure is not limited and can be controlled considering various conditions.

Though it is not illustrated in the figures, unevenness may be formed on covering portions 122 and 126 of the inner cavity structures to increase a human sensation of the shoes and aesthetic feeling.

The inner cavity structure may be filled with various materials. A filler of the inner cavity structure may be gaseous material such as an air or a material that is same as or different from the cross-linked foam body 120. If the number of the inner cavity structure is plural, each of the plural inner cavity structures may be filled with different materials. A phase of the filler is not limited and it may be gas, liquid or solid including a molded material. Those filler may be filled into an additional housing 160 and the housing may be disposed in the inner cavity structure. The FIG. 2 illustrates one of many possible embodiments in which the housing 160 filled with the filler 168 is formed in the inner cavity structure 128 for the metatarsus. The housing 160 may desirably be formed of a flexible material. That is, though the material for the hosing 160 is not confined to a certain material, it may desirably be formed of TPU (thermoplastic polyurethane). A reference number 162 is an injecting portion through which the filler is injected when the filler is injected into a space of the housing 160, and it is sealed after an injection process. A reference number 180 is a finishing material for the insole.

A manufacturing process of the cross-linked foam for an insole of the shoes comprises the following steps. In a first step, foaming material is prepared. In a second step, an interfacing pattern is formed on the foaming material. In a third step, the foaming material having the interfacing pattern goes through a cross-linked foaming process. In a fourth step, a shock-absorbing means is formed in the cross-linked foam. A step of re-molding may further be included in the manufacturing process.

The manufacturing method and process of the present invention will be described more in detail hereinafter with reference to attached figures. FIGS. 5 to 10 are illustrating a manufacturing process of an insole having a shock-absorbing means according to the present invention.

In the first step, a source material for the foaming material is selected from various materials such as the above mentioned materials for the cross-linked foam body 120 considering a use and a physical property of the cross-linked foam. After planning the material composition, the source material and the sub materials are weighed by desired amounts in accordance with the material composition plan, and then the source material and sub materials are mixed in the properly selected mixing device. The mixed chemical compound is then processed into a foaming material with a cross-linked foaming suppressed by a calender or an extruder.

The foaming material has a planar shape, such as film or sheet, or a three-dimensional shape, such as a pellet. The foaming material according to the present invention is not limited to a specific shape or type, but it may desirably have a planar shape, particularly a film shape, which has a low surface roughness, because the foaming material is weighed every time the foaming process is performed when it is used as a particle or sheet type. Further, when the foaming material is applied to the specific embodiment, the foaming material is recommended to have a planar shape, particularly a film shape, which has a low surface roughness, regarding the advisable use. If the obtained foaming material has a shape such as the pellet or the sheet having a rough surface, it may desirably be re-processed into a thin film having a low surface roughness. However, the shape of the foaming material is not limited as long as it can be processed into a certain shape with the cross-linked foaming suppressed and an interfacing pattern can be formed thereon later in the process. Though the foaming material 200 has a shape corresponding to the insole in FIG. 5, the foaming material of the present invention is not confined to this.

In the second step, at least one interfacing pattern is formed on the foaming material with different material from the foaming material to intercept a physical and chemical action among particles of the foaming material.

The material for the interfacing pattern may be liquids having viscosity, powder or solid having a certain shape such as films, which is able to prevent the interaction between the foaming materials during the cross-linked foaming process. For example, the interfacing material may be selected from a group consisting of natural or synthetic paints or inks, natural or synthetic resins, papers, textiles, non-woven fabrics, and rubbery materials. Additionally, when selecting the interfacing material, it is considerable to be easily attached to the foaming material, to have the repeated reappearance during the foaming process, to have the possibility of obstructing the cubical expansion of the foam during the foaming process, or to have the easy elimination from the cross-linked foam if required after the foaming process.

The formation of the interfacing pattern may be achieved by printing, transcription, coating, deposition, lamination, spray, cloth attachment, inserting, attaching or a modification thereof, and any other method can be possible only if it is able to form the interfacing material on the surface of the foaming material. However, when the ink or the like containing various kind of resins dissolved is used as an interfacing material, the printing method is desirably adopted in forming the interfacing pattern.

Further, if more than two interfacing patterns are formed, each of the interfacing patterns may be formed with same or different material. A foaming agent, which is the same as or different from a foaming agent contained in the foaming material, may be added to the interfacing material.

Moreover, a step of combining at least one foaming material having no interfacing pattern with the foaming material having the interfacing pattern may be further added.

The foaming material having no interfacing pattern may be the same material as or different material from the foaming material having the interfacing pattern. A step of adding material same as or different from the foaming material having the interfacing pattern to the combined foaming material may be further added.

There may be formed a plurality of interfacing patterns without a connection to each other, or all or some of the plural interfacing patterns may be connected to each other. Besides, the interfacing pattern may be connected only to the neighboring interfacing pattern.

In FIG. 5, two thin film type foaming material 200 is prepared and interfacing patterns 320 and 360 having a certain shape are formed on one of the foaming material 200. The interfacing pattern 360 is formed on the foaming material 200 at a position corresponding to the metatarsus of the feet and the interfacing pattern 320 is formed on the foaming material 200 at a position corresponding to the rest portion of the feet except the metatarsus.

A reference number 362 is an interfacing pattern for a cutting process that will be explained later. The interfacing pattern 362 for the cutting process is for opening the inner cavity structure 128 without damage to the cross-linked foam, i.e., the insole, during a cutting process of a portion of the insole.

In the third step, the cross-linked foam having a shape of the insole is formed by cross-linked foaming the foaming material having the interfacing pattern thereon. The cross-linked foaming of the foaming material may be performed by one of a pressure cross-linked foaming method and normal pressure cross-linked foaming method, or a modified or combined method thereof. But the cross-linked foaming method is not confined to those. In FIG. 5, a press type method using a molding die 400 is selected as one of the pressure cross-linked foaming methods.

If the heat is applied to the foaming material or if the electron rays are irradiated on the foaming material during the cross-linked foaming process, the foaming material is cross-linked in a gel state by the heat infliction or the electron irradiation. However, the foaming materials neighboring each other across the interfacing pattern are not physically/chemically coupled and interconnected until they reach the step of foaming. At this state, the foaming materials cubically expand at a specific rate and then the cross-linked foams are made as shown in FIG. 6.

As shown in FIGS. 6 to 7, portions of the foaming materials corresponding to the interfacing patterns 320 and 360 are also cubically expanded at the similar ratio to the other portions during the foaming process. However, because the physical and chemical connection of the foaming material is prevented by the interfacing pattern 320 and 360 and the interfacing pattern is foamed at a different ratio from the foaming material, a certain shape of space is formed in the cross-linked foam at a position corresponding to the interfacing pattern.

As shown in FIG. 7 illustrating a cross-sectional view of the cross-linked foam taken along a line D-D′ of FIG. 6, the spaces formed in the cross-linked foam body are inner cavity structures 124 and 128. Gases such as nitrogen (N₂) and carbon dioxide (CO₂) that is generated by a decomposition action of the foaming agent during the foaming process is trapped in the inner cavity structures 124 and 128 and thus keep the interior of the inner cavity structure at a certain pressure. The interior pressure of the gases in the inner cavity structures 124 and 128 can be properly controlled by adding a foaming agent to the interfacing material before the cross-linked foaming process.

The shape and structure of the inner cavity structures 124 and 128 and a projection of surfaces 122 and 126 of the cross-linked foam 100 can be modified diversely by controlling shapes of the interfacing patterns or changing interfacing materials regardless of shapes and kinds of the tools and devices for the cross-linked foaming process.

Though it is not shown in FIG. 5, unevenness may further be formed in a cavity 420 of the molding die 400.

In the fourth step, the shock-absorbing means is disposed in the cross-linked foam 100 for the sole. The disposing process of the shock-absorbing means mainly comprises following steps. In a first step, the inner cavity structure is open by cutting a portion of the inner cavity structure. In a second step, the housing is disposed in the inner cavity structure. In a third step, a filter is filled into the housing. In a fourth step, the housing is sealed. In a fifth step, the open portion of the inner cavity structure is closed.

A specific portion of the inner cavity structure 128 is cut to open the inner cavity structure 128 so that the housing can be introduced into the inner cavity structure 128. It is desirable that the cutting process be performed near a portion 127 of the inner cavity structure 128 that is formed by the interfacing pattern 362 shown as “a” in FIG. 7 to reduce a possibility of damage of the cross-linked foam body 120 and to make it easy to seal and close the open inner cavity structure 128.

As shown in FIG. 8, once the inner cavity structure 128 is open, the housing 160 in FIG. 4 is introduced into the open inner cavity structure 128 and then filled with the filler “b” by connecting an external injector 500 to an injecting portion 162 of the housing 160.

Once the filling process is completed, the injecting portion 162 is sealed using a high frequency or a supersonic waves, etc., as shown in FIG. 9, and then the open portions of the cross-linked foam body are closed by various attaching means such as a press machine shown as “C” in FIG. 10. Finally, an insole having a shock-absorbing means in FIG. 1 is obtained.

After the closing process of the open portion of the cross-linked foam body, the cross-linked foam 100 may be re-formed to treat an edge of the cross-linked foam 100 to be fit for the feet. Besides, the open portion of the cross-linked foam body 120 can be more firmly attached in the re-forming process.

While FIGS. 6 to 10 shows the case that an edge portion of the insole having a slope is formed to have a curved outline during the cross-linked foaming process, the tapered edge portion of the insole may be formed through a re-forming process after the cross-linked foaming process.

Unevenness may be formed in a cavity of a molding die for the re-forming process at a position corresponding the covering portions 122 and 126 or at an arbitrary position.

It will be apparent to those skilled in the art that various modifications and variations can be made in the cross-linked foam for the insole of shoes without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. 

1-13. (canceled)
 14. A cross-linked foam for an insole for shoes, comprising: a cross-linked foam body having at least one inner cavity structure, the inner cavity structure formed in the cross-linked foam body; a housing in the inner cavity structure, the housing filled with filler.
 15. The cross-linked foam according to claim 14, wherein the inner cavity structure having the housing is formed in the cross-linked foam body at a position corresponding to a metatarsus of a foot.
 16. The cross-linked foam according to claim 15, wherein unevenness is formed on a covering portion of the inner cavity structure.
 17. The cross-linked foam according to claim 14, wherein the filler is selected from at least one of gas, liquid and material that is same as or different from the cross-linked foam body.
 18. The cross-linked foam according to claim 14, wherein the cross-linked foam body further has at least one inner cavity structure other than the inner cavity structure having the housing.
 19. The cross-linked foam according to claim 18, wherein unevenness is formed on a covering portion of at least one of the inner cavity structures.
 20. The cross-linked foam according to claim 18, wherein the at least one inner cavity structure other than the inner cavity structure having the housing is filled with filler.
 21. The cross-linked foam according to claim 20, wherein the filler is selected from at least one of gas, liquid and material that is same as or different from the cross-linked foam body.
 22. The cross-linked foam according to claim 21, wherein the filler is filled into a housing and the housing is disposed in the inner cavity structure.
 23. The cross-linked foam according to claim 14, wherein the cross-linked foam body further has a plurality of inner cavity structures other than the inner cavity structure having the housing.
 24. The cross-linked foam according to claim 23, wherein at least one of the inner cavity structures other than the inner cavity structure having the housing is filled with filler.
 25. The cross-linked foam according to claim 24, wherein the filler is selected from at least one of gas, liquid and material that is same as or different from the cross-linked foam body.
 26. The cross-linked foam according to claim 25, wherein the filler is filled into a housing and the housing is disposed in the cavity structure.
 27. The cross-linked foam according to claim 23, wherein unevenness is formed on a covering portion of at least one of the inner cavity structures other than the inner cavity structure having the housing.
 28. The cross-linked foam according to claim 23, wherein all or some of the plural inner cavity structures are connected to each other.
 29. The cross-linked foam according to claim 28, wherein at least one of the inner cavity structures other than the inner cavity structure having the housing is filled with filler.
 30. The cross-linked foam according to claim 29, wherein the filler is selected from at least one of gas, liquid and material that is same as or different from the cross-linked foam body.
 31. The cross-linked foam according to claim 30, wherein the filler is filled into a housing and the housing is disposed in the inner cavity structure. 